Cable connection



June 1, 1965 E. w. BOLLMEIER 3,187,081

CABLE CONNECTION Original Filed Jan. 19, 1962 F/ci.

/0 l l llil I NVE N TOR. [m IVAY/YE 5014445151? Wd/ZQVM United StatesPatent 2 Claims. or. 174-211) This application is a division ofapplication Serial No. 167,380 filed January 19, 1962, now Patent No.3,150,221.

This invention relates to the connecting or splicing of segments ofsheathed cables and has particular reference to the splicing ofcommunications cables which are maintained under internal pneumaticpressure.

A typical form of telephone cable consists of a bundle ofplastic-insulated small copper wires wrapped loosely with a spiraled orlongitudinally lapped strip of plastic film and encased in a singleordouble-walled rubbery or plastic sheath having a metal foil shieldingmember within the outer sheath or between the two. The cable is commonlylaid underground, i.e. direct buried, being brought up at intervals, forexample to provide for splicing and for tapping of service wires atunpressurized road and access type pedestal cases. Entry of moistureinto such cables causes degradation of electrical characteristics andmust be avoided. To this end dry air is forced into the cable underpressure, and the pressure is continuously maintained. It is essentialthat adjacent cable-lengths be pneumatically inter-connected, e.g. atsplice and termination points, so that the air pressure may bemaintained throughout the entire cable.

Prior methods of gas-plugging the cable ends with self-hardening liquidresins and of forming pneumatic connections between cable-ends have beenless than fully satisfactory for a variety of reasons. Methods requiringperforation of the outer sheath have frequently resulted in damage tothe inner conductors. Methods involving end-wise insertion of permanentconnecting tubes into the wire-bundle have likewise resulted in wiredamage, or in ineffective flow of air pressure; or the method has beendifficult to practice due to the limited space available.

The present invention avoids these and other defects and disadvantagesof the prior art. There is provided a novel method for simultaneouslysealing and channeling cable-ends which is rapidly and efiicientlyfollowed without special training and with no danger of damage to cablecomponents, and in which are employed novel means for providingpneumatic connection with the cable interior.

The practice or" the invention will now be described in terms of theformation of an end seal in a plastic insulated telephone cable asillustrated in the accompanying drawing, in which FIGURE 1 is anelevation of an end seal area with portions cut away to show interiordetail, and FIGURE 2 illustrates the pneumatic interconnection ofadjacent sealed cable-ends.

The cable 1% is illustrated as consisting of a bundle of plastic-coatedcopper wires 11 spirally wrapped with an overlapping strip oftransparent plastic film 12 held loosely in place by a cord of untwistedfilaments 13, the whole being contained within an inner plastic sheath14, a rolled and longitudinally lapped fluted copper shield 15, and anouter plastic sheath 16. It will be appreciated that the number of wires11 is reduced for clarity of illustration; a cable of the structureshown and having an outer diameter of approximately inch may contain,for example, 18 pairs of color-coded polyethylene-coated No. 24 copperwires.

An open-ended conical container 17 is first placed over the end of thecable. The smaller open end of the conhatented June 1, 1965 tainer fitssnugly onto the outer sheath 16 and is slidable thereon. A terminallyexteriorly threaded tubular metal tap 2d, about /4 inch in diameter and2 /2 inches in length, and which may optionally be knurled or otherwiseroughened over its remaining length, is placed over an elongatemoderately curved wire probe 19 the forward portion of which is theninserted within the open end of the cable, e.g., between the plasticfilm 12 and the inner sheath 14 of the cable as shown, or, in a looselypacked cable, centrally of the bundle of wires. The end of the tap 20 islocated close to, but not necessarily in contact with, the end of thecable sheath. A wire 21 is connected to the shield 15 either bysoldering or by suitable clip means. The container 17 is then slid intoposition at the end of the sheath as shown, and an encapsulatingself-curing liquid resin is poured into the container and permitted toharden, forming the insulating and sealing resinous filler 18. The resinpenetrates around and along the individual wires 11, and around theprobe 19 and between the sheath 14 and film 12, but to a distancesomewhat short of the end of the probe, and sufficient resin is suppliedto cover a substantial portion of the length of the tap 20.

in place of the slidable one-part container 17 it will be appreciatedthat a split mold of the same general shape may be used, the segmentbeing snapped or otherwise held together around the previously preparedcable-end; or the one-piece mold may be applied after the probe memberis in place provided the mold opening will pass over the addedcomponents.

After the resin has hardened, the probe 19 is twisted to and fro bymeans of the handle 22 until it is broken loose from the surroundingresin. It is thenwithdrawn, leaving an open channel to the sealedinterior of the cable 10 from the threaded tap 20. Pneumaticinterconnection between cable-ends is then easily accomplished by meansof flexible hose 23 fitted at both ends, with appropriately threadedcouplings 24 for connection to the terminally threaded taps, or withother connecting means where non-threaded taps are employed. Thewire-ends are connected or tapped as desired, the ground connection iscompleted through conductor 21, and the entire connection enclosed in aweather-tight junction box or other protective covering.

An elfective probe for use with an l8-pair cable as herein described isprepared from a section of steel piano wire of about 2 mm. (.090 inch)diameter and about 10 inches in length, moderately uniformly curved to aradius of about one foot. The leading end of the probe is smoothlyrounded to avoid any cutting or tearing of insulation during insertioninto the cable. The wire is lightly wiped with a resin-resistantlubricant, preferably a silicone oil or grease, for ease in removal andfor rust prevention prior to use. The wire is curved sufficiently toposition the tap at an angle to the cable axis but not enough to causeany difiiculty either in placing the probe in the cable-end or in laterwithdrawing it from the tap.

An elfective resinous encapsulating composition consists of aself-curing mixture of liquid epoxy resin, liquid polysulfide polymer,and liquid amine catalyst. Typical compositions and means for mixinghave been described, for example in my U.S. Patent No. 2,877,288 whereinis illustrated another means of forming a pneumatic connection betweenelectrically connected sheathed cables. The components are mixedtogether just prior to application, to form a penetrating but moderatelyviscous liquid which rapidly cures to a strongly adherent tough andleakproof insulating resin.

The tap 20 fits loosely over the probe 19 and the resin rises within itto essentially the same level as within the container 17. The outersurface of the tap is securely gripped by the resin 18 so that thetwisting force required to loosen the probe is insufiicient to cause anyloosen- 7 ing of the tap within the encapsulating resinous mass.Pre-formed plastic or resinous taps may be substituted for the metal tap19. Although taps and probes of larger diameter may be used with largercables, it is equally elfective, and usually preferable, to employinstead a plurality of parts of the size indicated, the probe being ofapproximately the same diameter as the insulated wires of the cable andaccordingly fitting alongside such wires in the wire-bundle, and outsideof the plastic film 12, without developing any deleterious strains.Smaller components may be used but the size indicated is preferred asproviding adequate air flow together with sufficient strength for easyremoval of the probe.

The effort required to release and remove the probe is surprisinglysmall in view of the known strength of bond attained with the preferredresinous encapsulating agents. The release coating of silicone or othergrease is partly responsible, and the slight rubberiness orstretchability of the resin is also believed to play a significant part.In any event, it is found possible to release and remove the probe bysimple hand twisting and pulling after the resin has completely cured,leaving a permanent effective pneumatic connection to the interior ofthe otherwise hermetically sealed cable segment.

What is claimed is as follows:

1. A terminally gas-plugged shielded and sheathed communications cablehaving a large number of small insulated wires compactly bundledtogether within an enclosing insulating film, an intermediate closelyfitting surrounding flexible metal shield, and a closely fittingoutermost plastic sheath; said film, shield and sheath terminatingwithin a close-fitting outwardly flaring openended container, the freeends of the said wires extending beyond the open end thereof; a mass ofresinous filler filling the closed end of said container, surroundingsaid wires in a zone adjacent the closed end of said container,

and plugging the cable against passage of gas there through; at leastone elongate tubular tap terminally embedded and sealed within said massof resinous filler and supported thereby; the resinous filler having anelongate narrow opening therethrough interconnecting the interior ofsaid cable and the tubular tap.

2. A communications system comprising a series of cable segments havinga large number of terminally interconnected and exteriorly connectedsmall insulated wires compactly bundled together in each of saidsegments within an enclosing closely fitting flexible coveringcomprising a wrapping of insulating film, a wrapped thin metal shield,and a tubular plastic sheath, said covering terminating at each end ofeach segment Within a closefitting outwardly flaring open-top container,the Wires at each said end extending beyond the flared open end of saidcontainer; a mass of resinous filler filling the closed end portion ofeach said container, surrounding the wires, and plugging the cableagainst passage of gas; an elongate tubular tap terminally embedded andsealed within each said mass of resinous filler and supported thereby;said mass having an elongate narrow opening therethrough interconnectingthe interior of said cable section and the tubular tap; and flexibletubing interconnecting the taps of adjacent cable-ends within saidsystem to provide continuous pneumatic interconnection along the saidsystem.

References Cited-by the Examiner UNITED STATES PATENTS 2,711,438 6/55Bissell 17477 X FOREIGN PATENTS 1,059,527 6/59 Germany.

E. JAMES SAX, Primary Examiner.

JOHN P. WILDMAN, LARAMIE E. ASKIN, Examiners.

1. A TEMINALLY GAS-PLUGGED SHIELDED AND SHEATHED COMMUNICATIONS CABLEHAVING A LARGE NUMBER OF SMALL INSUALTED WIRES COMPACTLY BUNDLEDTOGETHER WITHIN AN ENCLOSING INSULATING FILM, AN INTERMEDIATE CLOSELYFITTING SURROUNDING FLEXIBLE METAL SHIELD, AND CLOSELY FITTING OUTERMOSTPLASTIC SHEATH; SAID FILM, SHIELD AND SHEATH TERMINATING WITHIN ACLOSE-FITTING OUTWARDLY FLARING OPENENDED CONTAINER, THE FREE ENDS OFTHE SAID WIRES EXTENDING BEYOND THE OPEN END THEREOF; A MASS OF RESINOUSFILLER FILLING THE CLOSED END OF SAID CONTAINER, SURROUNDING SAID WIRESIN A ZONE ADJACNET THE CLOSED END OF SAID CONTAINER, AND PLUGGING THECABLE AGAINST PASSAGE OF GAS THERETHROUGH; AT LEAST ONE ELONGATE TUBULARTAP TERMINALLY EMBEDDED AND SEALED WITHIN SAID MASS OF RESINOUS FILLERAND SUPPORTED THEREBY; THE RESINOUS FILLER HAVING AN ELONGATE NARROWOPENING THERETHROUGH INTERCONNECTING THE INTERIOR OF SAID CABLE AND THETUBULAR TAP.